In recent living environments, convenience has been further improved by electronics, household electric appliances, in-vehicle devices, and the like which are equipped with a new function that is not found in the related art. As a background thereof, it can be said that an operation of a sensor function, which compensates the five senses of human beings, are a large portion. Increases in the number of these products have been significantly expected in a wide range of fields. Examples of a sensor include various sensors using a semiconductor, and various sensors including pressure sensors, flow rate sensors, a motion sensor, luminance sensors, distance measurement sensors, and the like have been made into products.
Among the sensors, an optical sensor including the luminance sensor has been frequently used, and has been spreading widely due to an increase in mounting on an illuminating device for an office or a house, a portable terminal, a computer, and the like for use accompanied with low power consumption. Products, on which the sensor component is mounted, have characteristics in which diversification of application, abundance of functions, and a design excellent in portability are favorable. In addition, a reduction in size, thickness, and cost, and high, reliability are required in all products without exception. Among these requirements, a requirement for a package occupies a large portion. According to this, in development of the package, application of the related ad or of new technologies has become increasingly important.
FIG. 14 is an example of a cross-sectional view of a packaged optical sensor. An optical sensor element 24 is mounted on an insulating substrate 22 on which an interconnection pattern 21 is formed through metallization, and a light-transmitting epoxy resin 29 is molded at the periphery of the optical sensor element 24 (FIG. 2 of Patent Document 1). A resin 23, which has a composition of blocking an infrared light beam, is provided in a layer shape to overlap a flat surface of an outer surface of the light-transmitting epoxy resin 29 in an immediate upward direction of the optical sensor element 24.
As the optical sensor element 24 that is mounted, a light reception sensor element is used. The interconnection pattern 21, which is obtained through metallization, is electrically connected to an electrode provided on an upper surface of the optical sensor element 24 through a wire 25, and is used as a connection terminal with an outer side. An electromotive force, which is generated by a light beam that is incident to the optical sensor element, is transmitted to an external connection terminal through the wire 25. Light beams, which are incident from an outer side in an immediate upward direction of the optical sensor element, are transmitted through the light-transmitting epoxy resin after an infrared light beam is blocked by the resin 23, and thus the optical sensor element is sensitive to light beams close to the spectral luminous efficacy properties of human beings.
However, in the package structure described in Patent Document 1, the entirety of the package structure is molded with a transparent light-transmitting resin. In addition, the resin, which has a composition of blocking the infrared light beam, is provided only at a part of the outer surface of the light-transmitting resin, which molds the periphery of the optical sensor element, in an immediate upward direction of the optical sensor element. Therefore, with respect to light beams which are incident from an oblique direction, or light beams which are incident from a lateral direction, it is difficult to block the infrared light beam. Accordingly, it is difficult for the optical sensor element to receive only light beams having characteristics on which the spectral luminous efficacy properties are reflected. According to this, it is difficult to obtain sufficient spectral luminous efficacy properties with respect to light beams which are incident from the lateral direction or the oblique direction. As a result, it is difficult to obtain the desired light reception characteristics.
The package in the related art has a structure in which the periphery of the optical sensor element is molded only with the light-transmitting epoxy resin. It is known that the light-transmitting epoxy resin is weak to heat, moisture, and ultraviolet rays. When decomposition deterioration occurs in the resin due to heat, discoloration of the resin also occurs along with the decomposition deterioration. The discoloration causes light absorption, and a decrease in the transmittance is caused to occur. Therefore, light beams, which are incident from an outer side, are attenuated. As a result, an intensity of the light received by the optical sensor element decreases, and this decrease leads to deterioration in the light reception sensitivity. In addition, when being continuously exposed to heat, the resin becomes brittle and peeling-off or cracking is likely to occur. According to this, a decrease in strength occurs, and light beams incident from an outer side are attenuated. As a result, the intensity of the light received by the optical sensor element decreases and light reception sensitivity also deteriorates.
In comparison to an epoxy resin which is typically used in sealing of an IC package and contains a large amount of silica filler, in the light-transmitting epoxy resin, filler such as silica, carbon, and alumina is not contained. Accordingly, the coefficient of expansion of the light-transmitting epoxy resin is not changed from an original value of the resin. Therefore, the coefficient of expansion is higher in comparison to a resin that contains the filler. In addition, in a thermal shock environment in which a high temperature and a low temperature are repeated, and a reflow atmosphere in which a resin is rapidly exposed to a high-temperature atmosphere, significant expansion and contraction occur in a mold resin, and these lead to peeling-off of the resin and occurrence of cracking. According to this, light beams, which are incident from an outer side, are attenuated, the intensity of the light received by the optical sensor element decreases, and partial breakage occurs in the mold resin. As a result, it is difficult to obtain high reliability.
In addition, in the resin that is provided on an outer surface of the light-transmitting mold resin to block an infrared light beam, there is a concern of deterioration in resin characteristics being also likely to occur due to heat or moisture. Particularly, in a case of a resin provided with a specific property of blocking the infrared light beam in accordance with characteristics of a portion, which is classified into a dye, in a composition and a structure of the resin, it is typically pointed out that characteristics tend to be unstable due to deterioration in a dye component with respect to an external factor such as heat and moisture. When both of the light-transmitting resin that molds the periphery of the optical sensor element, and the resin that blocks an infrared light beam deteriorate, a plurality of resin factors, which have an effect on the reliability, exist. As a result, it is difficult to obtain high reliability.
In addition, the epoxy resin contains a benzene ring in a resin structure. When the epoxy resin is continuously exposed to ultraviolet rays, the benzene ring is damaged and open-ring decomposition occurs. This represents resin decomposition, and the epoxy resin is decomposed by ultraviolet rays. As a result, it is difficult to obtain high reliability when considering that light beams, which are incident from an outer side, are attenuated, and this attenuation leads to a decrease in the intensity of the light received by the optical sensor element, and decomposition of the mold resin also occurs.
In addition, when miniaturization and thinning of the package are performed, the thickness of the mold resin further decreases. According to this, the peeling-off of the resin, the cracking, the discoloration, and the like are further likely to occur, and a decrease in mechanical strength or easiness of deformation also occurs. As a result, the reliability of the package is further likely to deteriorate.
In consideration of this situation, a method of attaining an improvement in reliability has been attempted even in the light-transmitting epoxy resin. Examples of the method include a method in which a sealing resin is filled with filler to improve strength and heat-resistant properties of the resin, and to decease the coefficient of expansion of the resin, and a method in which the resin is filled with a substance having an ultraviolet-ray absorbing effect or a light stabilizer to make a countermeasure for ultraviolet rays. When the resin is filled with the filler, there are an effect of improving strength against impact from an outer side of the resin and an effect of decreasing the coefficient of expansion. Accordingly, it is possible to attain an improvement in reliability of a product. In addition, when the substance having the ultraviolet-ray absorbing effect is introduced, in a case where the resin is exposed to ultraviolet rays, damage is mitigated, thereby obtaining an operation of retarding deterioration of the resin. In addition, a variation in spectral luminous efficacy properties or deterioration in the light reception sensitivity of the optical sensor element due to a resin factor such as decomposition, peeling-off, and cracking of the resin is mitigated. Accordingly, it is possible to realize a package that is stable in characteristics and has high reliability.